If you have not specified an editor with the SET EDITOR command,
    the EDIT command starts the Language-Sensitive Editor (LSE) in
    a spawned subprocess (if LSE is installed on your system). The
    typical (default) way to use the EDIT command is not to specify
    any parameters. In this case, the editing cursor is initially
    positioned at the beginning of the line that is centered in the
    currently selected debugger source display (the current source
    display).

    The SET EDITOR command provides options for starting different
    editors, either in a subprocess or through a callable interface.

    Related commands:

       (SET,SHOW) EDITOR
       (SET,SHOW,CANCEL) SOURCE